Move some player-specific data out of the bloated GameState class.

Have gameplay objects hold a PlayerState pointer instead of a PlayerNumber and indexing back into GameState.
This will simplify off-screen players (e.g. CPU ghosts, network replicated human players, >2 players using one NoteField)

stepmania/src/PlayerOptions.cpp

@@ -484,7 +484,7 @@ void PlayerOptions::ToggleOneTurn( Turn t )
 	m_bTurns[t] = !bWasOn;
 }
 
-float PlayerOptions::GetReversePercentForColumn( int iCol )
+float PlayerOptions::GetReversePercentForColumn( int iCol ) const
 {
 	float f = 0;
 	int iNumCols = GAMESTATE->GetCurrentStyle()->m_iColsPerPlayer;